JPS5849401A - Automatic and continuous evaporating and condensing method and apparatus - Google Patents

Abstract

The invention relates to a vaporization and condensation process for the fractionation of mixtures by continuously heating, in a circulation circuit, a clean heat transfer gas which is subsequently injected into a mixture to be fractionated (16), of which at least one liquid fraction, which has separated off by vaporization, is condensed and collected while the heat transfer gas returns to the circulation circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to automatic and continuous evaporation and condensation methods and apparatus.

Distillation and drying are two operations that involve the evaporation of volatile phases and are often used in the chemical and pharmaceutical industries. The method of carrying out the evaporation of the volatile phase depends on the technical point of view,
Thus, both from the amount of fractions and residues obtained and the difficulty of handling operations, and from the economic point of view, ie from the capital investment and operating costs, are decisive factors in the success of the operation.

In fact, it is the heat exchange surface across which the heat of evaporation is supplied that attracts the most attention. material, i.e. simple
Phase mixtures or heterogeneous, i.e. multiphasic, mixtures, such as suspensions, dispersions or slurries, are inter alia , or especially in the case of multiphase mixtures, when the heating surface contains substances that tend to coalesce into a paste, the heating surface may become prohibitively expensive or very easily impossible to continue evaporating. A state of adhesion is rapidly reached.

When the treated mixture contains substances that are flammable or highly sensitive to heat, heating is traditionally carried out using a heat transfer fluid, most commonly water, if appropriate in the form of steam; However, the fact of using double heat exchange only increases heat losses and therefore costs, but in this case there are problems with excessive thermal gradients of the mixture being treated, or due to contacting mixtures. No problems of adhesion of exchange surfaces arise.

A particular field of industrial activity where fouling of heat exchange surfaces is clearly unavoidable is the field of treatment of residues of paints, varnishes, printing inks and similar mixtures. Although the invention will be described with reference to this particular case due to the fact that this treatment is associated with the most extensive difficulties, the present invention is directed to an operation that offers the same advantages as solvent recovery in the treatment of these residues. clearly applicable to

Ecological legal regulations actually prohibit the large discharge of polluting solvents containing various chemicals into the environment, but factories are constantly required to install complex and expensive equipment to recover the solvents. Not all of us are prepared for this, so we have to rely on a special company. These companies distill solvents, obtained and used from a wide variety of sources, in large quantities and on a large scale, which may be distilled with new solvents from one particular source or from other sources. Substantial compositional differences are inevitable between the solvents used, and these difficulties make recycling an unreliable task in applications requiring solvents with very specific properties.

It is therefore desirable to have a unique device that recovers solvent in a way that is reliable, reproducible and easy to implement, and that always gives a recovered solvent of well-defined composition. , of obvious value to the user.

A system that can be considered for use is that of water vapor stripping, the principle of which is to inject water vapor into the mixture to be treated, thereby removing not only water vapor but also the vapor of the liquid to be recovered. The total pressure of this vapor phase is the sum of the partial pressure of water vapor and the partial pressure of the vapor of the other liquid, so when condensed, the other liquid is miscible with water. Whether or not a mixture of water and other liquids will be obtained. However,
As is immediately clear, the ratio of the partial pressure of water to the partial pressure of the liquid at ground level is such that the higher the boiling point of the other liquid (the more unsuitable it is for the other liquid; When the liquid has a very high boiling point, the volume to be treated becomes excessive, and secondly, in practice, complete extraction of the second liquid is not possible.

Ultimately, stripping off the water vapor leaves a residue that is not only not dry, but also still contains significant amounts of contaminated liquid.

A device is also known from Belgian Patent No. 806,805 in which the heat exchange surface is not solid but liquid, in the case in question the surface of a layer of oil or heat transfer liquid. This clearly prevents adhesion of solid surfaces. Although this method overcomes important difficulties, it is necessary to subsequently separate the solids from the oil, which also interacts with certain solid residues, e.g. resins, and -
May form a gel.

Another system that can be considered is a thin layer evaporation on a regularly scraped surface. This type of equipment is conveniently used in the food industry, but in the recovery of solvents from paint residues and other similar slurry residues, as the scraping of resins, such as polymerized epoxides, is not complete. Less reliable.

The heat exchange surface has the advantage of avoiding the disadvantages of the known systems mentioned above and because the heat exchange that supplies the required heat to the system is carried out by contacting the heat exchange surface with a clean heat transfer gas. An automatic and continuous evaporation and condensation method and apparatus based on the principle of cleanliness have been invented.

Therefore, the present invention provides continuous heating of a clean heat transfer gas in a circuit and injection of this heated heat transfer gas into a mixture to be fractionated to transfer the heat of the heat transfer gas to said mixture. releasing, thereby causing at least one liquid fraction to leave the mixture by evaporation, continuously condensing and collecting this evaporated fraction, and continuously recycling the heat transfer gas into the circulation circuit. Automatic and continuous evaporation and condensation method for fractionating mixtures, characterized in that:

According to a particular embodiment of the method, the heat transfer gas used has a critical temperature lower than the temperature at which the evaporated fraction condenses, so that when the evaporated fraction condenses, heat is separated from the evaporated fraction. Continuously recirculating the transmission gas into the circulation circuit.

According to a preferred embodiment of the method, the heat transfer gas consists of a portion of the evaporated fraction and condenses and collects the remainder of the evaporated fraction.

Operation can be carried out in a room maintained at atmospheric pressure, subatmospheric pressure or superatmospheric pressure.

The present invention also provides an evaporation chamber consisting of a compartment, said compartment comprising a device for introducing the mixture to be separated and a device for discharging the residue,
The evaporation chamber is surrounded by a gas outlet column, a heat transfer gas circulation circuit including a fan, the fan being able to suck in the heat transfer gas and supply it to the outlet line;
The outlet line passes through a heating device and has at its end a distributor that brings the heat transfer gas into contact with the mixture to be fractionated and is connected to the gas outlet column and evaporated in the evaporation chamber. The present invention relates to an apparatus for carrying out the method in its various embodiments, characterized in that it consists of a condenser suitable for condensing and collecting the fraction/s.

In a particular embodiment of the device, the device includes a heat transfer gas return line leading from the cooler to the fan.

According to a preferred embodiment of the device, the inlet of the fan communicates with the upper zone of the evaporation chamber, so that the fan can thus suck in a portion of the evaporated fraction formed within the evaporation chamber.

In order to prevent the gas circulation circuit from being contaminated by mechanical entrainment of liquid and solid particles, this device is advantageously located upstream of the cooler, and if the fan communicates with the upper zone of the evaporation chamber, Includes a mist separator, also located upstream of the fan.

When the fan communicates with the upper zone of the evaporation chamber, the entire heat transfer gas circulation circuit is preferably located inside the evaporation chamber.

However, according to a particular embodiment of the device, the heating device forming part of the heat transfer circuit is located outside the evaporation chamber.

In all embodiments of the device, the evaporation chamber is
The fact that it is protected against heat losses by one or more layers ensures very economical operation.

To ensure a high degree of safety even in the processing of mixtures with low flash points, the heating device is a steam heat exchanger,
The heat exchanger receives live steam through one line and returns cooler steam and/or condensed water through another line.

According to an advantageous embodiment of the device, the heated gas distributor is a nozzle manifold, which emits the heated gas with sufficient impact to move the contents of the compartment.

For operation under atmospheric pressure, subatmospheric pressure or overpressure, the device has a device for maintaining constant pressure.

In order to enable the equipment to function continuously for long periods of time, the compartment feeding device is a continuously operating device, and the device for removing the residue from the compartment is a continuously operating device for drying residues. It is a discharge device.

It is often sufficient that the supply of the compartment is continuous, while the residue removal device of the compartment is a simple manifold from which the dry residue can be withdrawn at the end of the operating period.

The invention will be further explained with reference to a special embodiment of this device suitable for treating paint residues, which is shown in the accompanying drawings.

The apparatus for carrying out the method of the invention, applied to the treatment of paint residues, comprises an evaporation chamber 2 protected by 80 layers of thermal insulation.
The evaporation chamber consists of a lower compartment 4 attached to a platform 5, which compartment number is equipped with a feed device 6 and a residue evacuation device 7 (the latter being in the form of a manhole in this case) and a gas outlet. The gas circulation circuit includes a fan 9 in the gas outlet column 8, which is operated by an electric motor lO, the inlet 11 of which is located in the upper part of the evaporation chamber 2, while The outlet line 12 of the fan passes through a heat exchanger 18 and has at its lower end a distributor 14 of heated gas, the nozzle 15 of which discharges the contents 1 of the compartment 4.
Finishes on top with a shorter distance than 6. Heat exchanger 18 is a steam exchanger that receives and takes live steam through line 17 and returns cooler steam and/or condensed water through line 18, these two lines being connected to gas outlet column 8. pass through the insulated wall. The gas circulation circuit is completed outside the evaporation chamber 2 by a cooler 19 suitable for condensing and collecting the evaporated fraction.

The cooler 19 receives the steam extracted from the upper part of the gas outlet column 8 from its inlet 20 near the intake port ll of the fan 9. At its lower end, the cooler 19
has a condensate outlet 21 as well as a device for maintaining a constant pressure in the device 1, and consists of a vacuum pump 22, which is connected to the cooler 19 by a three-way valve 28, and A three-way valve 28 connects the cooler 19 to the atmosphere and/or to a vacuum pump. The mist separator 24 is fixed in the gas outlet column 8 below the inlet 20 of the fan 9 and the cooler 19 and is therefore located upstream of the cooler and the fan.

The illustrated device is particularly suitable when the heated heat exchange gas consists of a part of the evaporated fraction, the remainder of which is condensed and collected, and a pasty and viscous residue, e.g. Particularly suitable for the treatment of paint, printing ink and face residues, which must be recovered. The intake 11 of the fan 9 is close to the inlet of the cooler 19, so that during operation of the device, the fraction of the vapor phase that is directed towards the heat exchanger 18 and the fraction of the vapor phase that condenses in the cooler 19. An allocation occurs between. Vacuum pump 22 is preferably a liquid-ring pump, and when it is in operation, the device operates under vacuum, and communication between the pump and the device is provided by three-way valve 2.
It is done by 8. However, the same device can operate at atmospheric pressure when the vacuum pump 22 is stopped, with appropriate adjustment of the valve 28. Due to the fact that the heat exchanger 18 is in contact with a clean gas phase, it remains clean and free of dirt.
Maintain excellent working condition. Moreover, due to the fact that the heat exchanger is fixed in an insulated chamber, heat losses are reduced to a minimum. Instead of the live steam exchanger 18, an electric heat exchanger can be used, which is specially designed to avoid the risk of explosion.

The gas return line 25 connects the space filled with the gas phase of the gas-liquid separator 26, which is attached to the outlet 21 of the cooler 19 and has a liquid outlet 27, to the intake of the fan 9 and, under operating conditions, It is possible to maintain a circulation of non-condensable gases, such as nitrogen, contaminated with very small amounts of vapor introduced at 27. The installation that makes it possible to carry out this embodiment, i.e. the return line 25 leading back to the fan 9, the gas/
Liquid separator 26 and liquid outlet 27 are shown in broken lines in the figure. Such an arrangement can, for example, contain styrene monomers that can polymerize when in contact with the hot surfaces of a heat exchanger.
An inert gas is used to allow it to be stripped and condensed without contaminating it with styrene monomer.

[Brief explanation of drawings]

The accompanying drawing is a schematic partial sectional view of an apparatus for carrying out the method of the invention. ■ Apparatus 2 Evaporation chamber 3 Insulation 4 Lower compartments 5 6 Supply device 7 Residue discharge device 8 Gas outlet column 9 Fan IO motor 11 Inlet 12 Outlet line 18 Heat exchanger 15 Nozzle 16 Contents 17 Line 18 Pipe line 19 Cooler 20 Population 21 Condensate outlet 22 Vacuum pump 28 Three-way valve 24 Mist separator 25 Gas return line 26 Gas-liquid separator 27 Liquid outlet JP-A-53-49401 (6) Procedural amendment book Showa Tough Year July 76th, Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office, 1, Indication of the Case Showa <2nd Year Patent Application No. NU/-I? No. 2, Relationship with the invention title case Patent applicant address 5, Subject of amendment

Claims (1)

[Claims] 1. Continuously heating a clean heat transfer gas in a circulation circuit,
This heated heat transfer gas is injected into the mixture (16) to be fractionated so that the heat of the heat transfer gas is released into said mixture so that at least one liquid fraction leaves said mixture by evaporation. Automatic and continuous evaporation and condensation method for fractionating mixtures, characterized in that this evaporated fraction is continuously condensed and collected, and the heat transfer gas is continuously recycled into the circulation circuit. 2. The heat transfer gas used has a critical temperature lower than the temperature at which the evaporated fraction condenses, so that when the evaporated fraction condenses, the heat transfer gas separating from the evaporated fraction 2. A method as claimed in claim 1, comprising continuous recirculation into the circulation circuit. 8. The method of claim 1, wherein the heat transfer gas comprises a portion of the vaporized fraction, and the remainder of the vaporized fraction is condensed and collected. 4. The method according to any one of claims 1 to 8, wherein the operation is carried out in a chamber (2) maintained at atmospheric pressure. 5. The method according to claim 1, 2 or 8, wherein the operation is carried out in a chamber maintained at reduced pressure. 6. The method according to claim 1, 2 or 8, wherein the operation is carried out in a chamber (2) maintained at overpressure. 7. An evaporation chamber consisting of a compartment (4), said compartment (4) having a feeding device (
6) and a device (7) for discharging the residue, the evaporation chamber 0
) is surrounded by a gas outlet column (8),
a heat transfer gas circulation circuit comprising a fan (9), said fan (
9) sucks in the heat transfer gas and sends it to the outlet line (12)
), and the outlet line is connected to a heating device (1
8) and has at its end a distributor (14), said distributor (14) distributing the heat transfer gas to the contents of the compartment (1).
6) and a condenser (19) connected to the gas output ram (8) and suitable for condensing and collecting the fraction evaporated in the evaporation chamber (2). An apparatus for carrying out the method according to any one of claims 1 to 6. 8. includes a heat transfer gas return line (25), said return line from a gas/liquid separator (2) attached to said cooler outlet (21) to said fan (9); 8. The device of claim 7, as claimed in the accompanying claim. 9. Apparatus according to claim 8, comprising a mist separator (24) located upstream of the cooler (19).・The inlet (l l) of the fan (9) is the evaporation chamber (2)
8. A device according to claim 7, in which said fan (9) is in communication with the upper zone of the evaporation chamber (2) and is capable of sucking in a portion of the evaporated 7-lux thus formed in the evaporation chamber (2). (2) upstream of the cooler (19) and the fan (9);
11. Apparatus according to claim 10, including a mist separator (24) located upstream of the mist separator (24). 12. Apparatus according to claim 10 or 11, wherein the entire heat transfer gas circulation circuit (P) is located inside the evaporation chamber (G). B. The device according to claim 10 or 11, wherein the heating device (18) is located outside the evaporation chamber (2). 19. The device according to any of claims 7 to 18, wherein the evaporation chamber 0) is insulated by one or more layers of heat insulating material (8). b. Said heating device (18) is a steam heat exchanger, said heat exchanger receiving live steam through one line and transferring cooler steam and/or condensed water through another line (
18) The device according to any one of claims 7 to 18. The distributor (14) is a nozzle manifold (15), which releases the heated gas with sufficient impact to move the contents (16) of the compartment (→). 16. Apparatus according to any of claims 7 to 15. 17. Apparatus for maintaining a constant pressure and comprising a vacuum pump (22), said vacuum pump being connected to said cooler (19).
) by a three-way valve (25), and said three-way valve connects said cooler (19) to atmospheric pressure and/or to said pump (22).
17. Apparatus according to any one of paragraphs 16 to 16. Claims 7 to 17, wherein the feeding device (16) is a continuously operating device and the residue outlet device (7) is a continuously operating dry residue outlet device.
Apparatus according to any of paragraphs. Claims 7 to 17, wherein the feeding device (6) is a continuously operating device and the residue outlet device (7) is a discontinuously operating dry residue outlet device.
Apparatus according to any of paragraphs.